Sinclair met Sheridan during a series of Mars riots (there were several outbreaks at different times before the series starts up), but I'm not sure he met Garibaldi at that time. As far as I can remember the first time Garibaldi met Sinclair was when they stumbled across the first Shadow ship that was excavated on Mars in 2253. Sinclair hired Garibaldi as a pilot to take some kind of team out to the Martian desert and their flyer crashed. I think they were the only two survivors, both were injured, and it took them some time to walk out of the wastelands to get help. (The story is told in part in the S3 episode "Messages from Earth", although I think Garibaldi keeps Sinclair's name out of it. It is also told in one of the B5 comic books.)
Not a long acquaintance, but the kind of intense experience that causes people to get to know each other very well, very quickly. They saved each other's lives more than once on the return journey, and that can form a life-long bond between people even if they never see each other again and only communicate by letter or phone. Lise may have been exaggerating their lack of contact (they may only have "met" twice in person, but stayed in touch by other means) in order to score points in the argument with Garibaldi.
I would imagine that their second meeting was when Sinclair came to Mars to ask Garibaldi to join him on B5. Obviously he remembered him well, and it would only have been three or four years after their first meeting.
Also don't forget, by the time "Infection" rolls around, both Garibaldi and Sinclair have been working together aboard B5 for nearly a year. Long enough for them to have learned a lot about each other's histories, including their past relationships. Sinclair may have met Lise on Mars, and even if Garibaldi never met Catherine Sakai, which he may have done after he and Sinclair made it back to Marsdome when they first met, he probably saw her picture many times in Sinclair's quarters. So he'd have no trouble recognizing her when she came aboard, and he'd certainly know her history with Sinclair. Heck, Sinclair has already developed a close relationship with Delenn in The Gathering and the station has only been operational for a few months at that point. Unlike Garibaldi he seems to have a knack for friendship. /forums/images/graemlins/smile.gif
Regards,
Joe
